Qhov tsis tu ncua ntawm cov dej tshiab, lim dej uas tau muab los ntawm peb qhov kev pom (activated carbon, ion exchange resin, thiab non-woven fabric) txhawb cov tsiaj kom haus ntau dua, txhawb lawv txoj kev noj qab haus huv tag nrho.Cov dej ntws tsis tu ncua yog lim thiab oxygenated, muab qhov siab tshaj plaws freshness.